The present invention relates to friction plate facings which are conventionally bonded to metal plates or cores which are then incorporated into interleaved clutch packs. The clutch packs, generally, are interconnected with inner hubs and outer drums of a clutch assembly and are commonly engaged and disengaged through the use of a hydraulically or spring actuated piston. The typical friction disc used in such clutch packs commonly incorporates an annular steel ring or core and a pair of friction facings which are bonded to the opposed sides of the core. The friction facings are commonly blanked out as one piece rings from continuous rolls of friction material such as a sintered metal or paper impregnated with a resin which is fed through a blanking press. As the costs of such friction paper raw material increase and as industry becomes more accountable for its scrap and the need to properly dispose of the scrap, it has become a major objective to economize the amounts of friction paper utilized in manufacturing friction facings and, concomitantly, reduce the amount of scrap or offal remaining without compromising the strength or integrity of the end product friction ring.
U.S. Pat. No. 4,260,047, issued to Nels, represents one of the first proposed solutions for achieving greater economy in the manufacture of friction facings. Nels provides four ninety degree arcuate segments stamped from a rectangular sheet of pregrooved friction material. The segments are interconnected by opposed tab and slot structures to form a complete annular friction facing which is then bonded onto an annular metal core. The approach of Nels was further improved upon by Mannino in U.S. Pat. No. 4,674,616 wherein the annular core plate or steel plate is also segmented with interlocking end portions to form the annular ring to which the segmented facings are bonded. The Nels and Mannino approaches have achieved a first step in reducing the waste amounts of friction material and the waste amounts of steel in the manufacture of friction discs for use in clutch packs.
It has been discovered, however, that the match lines or junctions formed between the facing segments when the arcuate segmented facings are interjoined to create the annular ring create areas of structural weakness in the overall integrity of the friction facing. It has been particularly noticed that match lines or junctions which are disposed ninety degrees apart suffer the greatest potential for premature failure. Further, the opposed tab/slot configurations utilized by the facings of the type shown in Nels and Mannino have shown a tendency to isolate the forces applied to the match lines on the facings to specific fragile areas of interconnection. This tendency may then also increase the potential for premature failure. Thus, it is an object of the present invention to significantly reduce the amounts of friction paper utilized in the manufacture of friction facings without compromising the structural integrity of the final annular friction ring product.
It is another object of the invention to further economize the manufacture of friction face by further reducing the production of scrap material to minimal amounts.
It is a further object of the invention to reduce the number of match lines in a formed annular friction facing, thereby reducing the potential for premature failure.
It is yet another object of the invention to eliminate match lines located at ninety degree intervals.
Yet another object of the invention is to provide for a unique tab and slot configuration at each end of each facing segment which interlocks with the tab and slot configuration on an adjacent segment and provides opposing forces on the match line between the segments which emanate from the center of each match line.
It is yet another object of the invention to provide that the opposing faces on the match line provide resistance to forces applied in multiple directions.
Finally, it is an object of the invention to provide for further reinforcement of the match line area to prevent potential damage to the friction material prior to the final bonding of the friction facing to the annular core.